Tow guide



July l1, 1961 R. H. BECKER ET AL TOW GUIDE Filed Oct. 26, 1959 A T TOR/V5 7 United States Patent O y 2,991,502 TOW GUIDE Y Robert Harbes Becker, Douglas Lewellyn Johnson, and William Thomas Martin, Pensacola, Fla., assignors to American Cyanamid Company, New Y'ork, N.Y., a corporation of Maine Filed Oct. 26, 1959, Ser. No. 848,843 Claims. (Cl. 18-8) This invention relates to a tow-guide assembly, and more particularly to apparatus adapted to be used in improving post-extrusion, speciiically coagulating and handling conditions, of freshly formed, synthetic fiber tow. Still more particularly, this invention relates to a device for guiding and withdrawing synthetic liber tow from a coagulating bath which comprises a means for main taining a synthetic tiber Itow in uniform contact with the coagulating solution until -it is discharged and a discharging -means which provides for drawing off the tow with a amount of adhering solution.

In the production of fibers by a wet-spinning process, the ftberor filament-forming material is extruded as a solution (e.g., a solution of polyacrylom'trile dissolved in a concentrated aqueous solution of a thiocyanate such as calcium Ithiocyanate) into a coagulating 'bath through multi-hole spinnerettes which form a iibrous shape. As the spinning solution enters the coagulating bath (e.g., water) it precipitates into gelled multitilaments or tow. It is important that this tow be in contact with the coagulating solution for an adequate time in order to be sufficiently precipitated. After Ithe tow has been in contact with the coagulating solution for the necessary length of time, it is then continuously withdrawn from the coagulating bath for further processing. As the tow is discharged, however, it has been observed that gravity produces a dip in the tow as it comes from the coagulating bath, thereby causing the adhering coagul-ating solution to travel along with the tow. Some of this adhering solution is eventually re-absorbed by the synthetic iiber tow. This is especially undesirable because of the resulting loss of solution containing valuable solvent, eg., aqueous thiocyanate solution. In order to overcome these undesirable features, applicants have made the present invention. Nowhere in the prior art is there disclosed a device which is similar to that taught by applicants.

In the past, horizontal rods traversing the direction ilow of the tow, or ceramic parts containing small apertures which tend to converge the individual filaments. of the tow, were employed as discharging means.

'Fwo notable disadvantages in the use of these prior art devices are that there is considerable damage caused to the filaments themselves and that the converged tow is not suihciently contacted by the coagulating solution to get complete precipitation. This results in a subsequent fusion of the fibers to one another. Applicants have found that by passing the tow over an arcuate spreading means as it is drawn from the coagulating bath, the tow is maintained in uniform contact with the coagulating solution which is drawn with the liber tow as it leaves the coagulating bath. After .the tow has passed along a sufficient length of this arcuate spreading means, it is then suiiiciently precipitated to be transferred to its next step. In order to alleviate the above-mentioned problem of the ladhering coagulating solution, applicants found that an upwardly-inclined, arcuate discharging device was effective. This arcuate discharging device not only causes the adhering coagulating solution to be separated from the tow, but yalso insures sufficient spreading of the tow as it travels across the arcuate spreading means. The use of this device provides for control of the im- ICC mersion time of the filaments in the coagulating solution and independently discharging the solid from the liquid. In addition to these, the solid filaments do not drag on any rough surfaces and the ilow of liquid is uniform and, therefore, minimizes breakage of the filaments.

For a better understanding of the present invention, reference may be had to the accompanying drawing in which:

1 FIGURE 1 is a perspective view of the tow-guide assembly.

FIGURE 2 is a perspective view of the tow-spreading means.

yFIGURE 3 is a perspective view of the tow-discharging means.

FIGURE 4 is a perspective View of a sloped weir.

VFIGURE 5 is a plan view of the tow-guide assembly, together with the tow coming from the spinnerettes over the tow guide and around the capstans for further treatment.

FIGURE 6 is a side view of the tow being extruded into the coagulating bath from the spinnerettes and being drawn up the tow guide.

The structure of the tow-guiding and discharging assembly is clearly set forth in FIGURES 1 4 of the drawing. The invention as shown in FIGURE l comprises an upwardly inclined ramp 1 which is attached at its upper end to a horizontal trough 2. 4Both the ramp and the trough are bounded on each side by walls 3 which are coextensive with the entire length of each side of the structure. The wall portions of the horizontal trough are raised to maintain the level of solution above the tow and channel the solution over the downstream end. Mounted on the upper end of ramp 1 is approaching planar surface 4 longitudinally extending at an increased inclination from the upper section of the ramp 1. Spanning the upstream end of horizontal trough 2 and extending over a substantial length of the trough is arcu` ate tow-spreading means 5, which forms a section fromv a cylinder not necessarily -generated from the circle.V

Longitudinally extending surface 4 terminates in an elliptical or circular arc formed by the plane of surface 4 cutting cylindrical section 6. FIGURE 2. clearly sets forth the structure of the tow-spreading means where the approaching surface is planar. Mounted downstream and spaced lfrom tow-spreading means 5 is an upwardly inclined arcuate towdischarging means 7, spanning the width of trough 2 and extending at least above the level of tow-spreading means 5. Beneath the discharging means is an open area providing a zone which is in liquid communication withboth ends of said trough 2.

Located in said zone is an upwardly sloped Weir 9 extending the full Width of the open area. The terminal end of horizontal trough 2 may be extended on one side with depending element 8 to channel the coagulating solutions which pass over Weir 9 into a duct for recycling back to the coagulating baths. URE 5.)

FIGURES 5 and 6 clearly illustrate the use of the present invention for discharging the brous tow. These` figures show the tow 10 passing up ramp 1, over spreading means 5, discharging means 7 and the coagulatingV merges with arcuate tow-spreading means 5. As clearly (See element 11, FIG- illustrated in 'FIGURE 5, the tow is then spread to provide uniform contact with the adhering solution and is maintained in this condition for a predetermined amount of time which is controlled by the length of tow-spreading means S, thereby insuring complete precipitation. The tow is then discharged over the upwardly inclined towdischarging means 7. As the tow travels up the inclined surface of the discharging means, the excess adhering coagulating solution runs back into trough 2 and the tow is then discharged with a minimum amount of adhering solution.

Upwardly sloped weir 9, which may be placed beneath tow-discharging means 7 or further downstream, serves the dual function of maintaining the level of this separated solution and at the same time is sloped in such a way that particles of dirt are automatically discharged over the weir` with the excess solution and into the return duct 11 by way of element 8.

The size and shape of applicants device may vary widely so as to be adapted to various operations which depend on size and type of polymer filament-forming material which is used to produce the liber. The only critical `features of the device are the inclinations or slopes of the ramp 1 and the discharging means 7, and the radius of the arc of the discharging means 7 and towspreading means 5. The inclination or slope of ramp 1 cannot be so steep that the newly coagulated tow is distorted or torn, while at the same time it should be suiciently inclined to keep the trough from flooding. Applicants have found that a slope within the range of from about 15 to 45 from the horizontal is operative but this may be extended in either direction for certain tows which may coagulate either very fast or very slowly. The slope of the discharging means 7 can be varied within the above range, but as the slope is increased there is a tendency for the tow to ride on the discharging edge, and there is also premature separation from the coagulating solution in the trough 2. Preferably the angle should be within the range of from about 25 to 35 from the horizontal. The radius of the arc of the spreading means 6 is not too critical, but it should not be less than about 5 inches. `In some instances, the arc may have very large radius if the tow is fragile and is suiciently spread by the arc of the discharging means 7. In an extreme case the arc may have an infinite radius and the trough would, therefore, have a at bottom. It is preferred, however, that the radius of the arc fall within the range of from about inches to about 25 inches. The degree of arc for the discharge means 7 is critical and should have a radius within the range of from l0 to 20 inches and preferably within the range of from about 13 inches to about 17 inches. 'I'he slope of weir 9 is not critical, but it should not exceed 65 or 75 because the solution at the bottom tends to become static and any dirt present will not be Washed over the weir. The height of the weir is, of course, dependent on the size of the tow. The purpose of the weir, as has been indicated hereinbefore, is to insure the level of the coagulating solution above the tow.

The overall dimensions are not critical and may be varied considerably for each individual case. For an efficient design, the tow-discharging means 7 should not be spaced any further than is necessary from the towspreading means 5. That is, the tow should not dip oif the end of the spreading means but it should extend upward onto discharging means 7. The angle that the approaching surface 4 of the spreadingmeans makes with ramp lis negligible and is only an'engineering expediency, since it is desirable to have the spreading meansa separate unit from the remaining structure for cleaning purposes, etc. Though the other means are also separate units, it is entirely conceivable that the entire device may be constructed as an integral unit.

The above described tow guide may be used inthe production of any type fiber or filament formed from a wet-spinning process. They include all vinyl polymers and copolymers such as acrylics and polyvinyl chloride, polyesters and other condensation type polymers which can be adapted to such a process.

We claim:

1. A tow-guide assembly adapted to guide tow during withdrawal from a coagulating bath comprising an up- Wardly inclined ramp for receiving and directing the flow of said tow, said ramp being longitudinally aligned with and fixedly attached at its upper end to one end of a horizontal tow-discharging trough, said discharging trough including an arcuate tow-spreading means spanning said one end for maintaining complete contact between the tow and the coagulating solution as the tow with adhering solution is drawn up the inclined ramp and into the discharging trough; an upwardly inclined arcuate discharging means for drawing off said tow with a minimum amount of adhering solution, said discharging means being spaced downstream from said tow-spreading means and providing an enclosed zone; and an upwardly sloped weir located in said zone and whereby excess solution is discharged over said weir.

2. A tow-guide assembly as in claim 1 wherein the upwardly inclined arcuate discharging means has a slope within the range of from about 15 to about 45 from the horizontal.

3. A tow-guide assembly as in claim 2 wherein the arc of said discharging means has a radius falling within the range of from about l0 inches to about 20 inches.

4. A tow-guide assembly adapted for use in the production of a tow of lamentary material by extruding a iilament-formable solution into a coagulating bath, said assembly comprising an upwardly inclined ramp for receiving and directing the moving tow, said ramp having mounted on its upper end an approaching planar surface that longitudinally extends at an increased inclination from the upper section of said ramp; a horizontal towdischarging trough aligned with and iixedly attached at one end to the upper end of said planar surface; an arcuate tow-spreading means spanning one end of said tow-discharging trough for maintaining complete contact between the tow and the coagulating solution as the tow with adhering solution is drawn up the said inclined ramp, and also up the approaching planar surface mounted on the upper end of said ramp, and thence into the said dscharging Itrough; an upwardly inclined arcuate discharging means for drawing off said tow with a minimum amount of adhering solution, said discharging means being spaced downstream from said tow-spreading means and providing an enclosed zone; and an upwardly sloped weir located in said enclosed zone beneath said upwardly inclined arcuate discharging means and whereby excess solution is discharged over said weir.

5. A tow-guide assembly adapted for use in the production of a tow of filamentary material by extruding a lament-formable solution into a coagulating bath, said assembly comprising an upwardly inclined ramp for receiving and directing the flow of said tow, said ramp having mounted on its upward end an approaching planar surface that longitudinally extends at an increased inclination from the upper section of said ramp; a horizontal tow-discharging trough aligned with and xedly attached at one end to the upper end of said planar surface; an arcuate tow-spreading means spanning one end of said tow-discharging trough for maintaining complete contact between the tow and the coagulating solution as the tow with adhering solution is drawn up the said inclined ramp, and also up -the approaching planar surface mounted on the upper end of said ramp, and thence into the said discharging trough; an upwardly inclined arcuate discharging means for drawing off said tow with a minimum amount of adhering solution, said discharging means being spaced downstream from said towspreading means, having a slope within the range of from about 25 to 35 from the horizontal, and providing an enclosed zone; an upwardly sloped Weir located in said enclosed zone beneath said upwardly inclined arcuate discharging means and whereby excess solution is discharged over said Weir; and a depending element extending on one end of the terminal end of the said horizontal tow-discharging trough for channeling coagulating solution that passes over the aforesaid Weir into a duet for recycling back to the said coagulating bath.

References Cited in the le of this patent UNITED STATES PATENTS Taylor Apr. 7, 1936 Hofmann Mar. 4, 1952 Rarick Nov. 17, 1953 Schmitz Apr. 2, 1957 Sonnino Sept. 2, 1958 

